Composite fluid dynamic bearing and its manufacturing method

Abstract

A composite fluid dynamic bearing and its manufacturing method is disclosed. By machining a plurality of bearings independently, the grooves of each bearing have uniform slopes. Then the method of the invention combines the bearings, which have different slope of the grooves, to form a bearing module having pressure-generating grooves. In this way the precision of the machining grooves of bearings can be improved.

What is claimed is:  
     
       1. A composite fluid dynamic bearing for housing a spindle and providing a fluid dynamic pressure to support the spindle when the spindle rotates, comprising: 
       a bearing seat having an inner through hole; and  
       at least one bearing set having an inner hole with a diameter slightly greater than the spindle and an outside diameter substantially same as the inner hole of the bearing seat and to be housed therein, each bearing set including a plurality of bearings that have grooves of different slopes formed on the surface of the inner holes thereof to form pressure-generating grooves, the grooves formed on the surface of the inner hole of each bearing having substantially a uniform slope.  
     
     
       2. The composite fluid dynamic bearing of  claim 1 , wherein the grooves on the surface of the inner hole of the bearing are helical grooves of a uniform slope. 
     
     
       3. The composite fluid dynamic bearing of  claim 2 , wherein the helical grooves form herringbone pressure-generating dynamic grooves by coupling the bearing sets that have the helical grooves formed in different directions. 
     
     
       4. The composite fluid dynamic bearing of  claim 1 , wherein the bearing sets are interposed by a spacer, the spacer having an inner diameter same as the bearing. 
     
     
       5. The composite fluid dynamic bearing of  claim 1 , wherein the bearing sets are selectively installed in the bearing seat by bonding, pressing, or welding. 
     
     
       6. A method for manufacturing a composite fluid dynamic bearing, comprising steps of: 
       providing a plurality of bearings that have grooves of different slopes formed on the surface of the inner holes thereof, the grooves on each bearing having substantially a uniform slope;  
       coupling the bearings alternately; and  
       installing the bearings in a bearing seat.  
     
     
       7. The method of  claim 6 , wherein the step of providing a plurality of bearings that have grooves of different slopes formed on the inner holes thereof is accomplished by machining respectively inner grooves of different directions on bearings of desired lengths. 
     
     
       8. The method of  claim 7 , wherein the step of machining respectively inner grooves of different directions on bearings of desired lengths is followed by cutting the bearings to smaller sections. 
     
     
       9. The method of  claim 7 , wherein the grooves formed on the surface of the inner holes are helical grooves. 
     
     
       10. The method of  claim 9 , wherein the helical grooves are formed in different directions alternately. 
     
     
       11. The method of  claim 10 , wherein the pressure-generating grooves are herringbone grooves. 
     
     
       12. The method of  claim 6 , wherein the step of coupling the bearings alternately includes installing a spacer. 
     
     
       13. The method of  claim 6 , wherein the spacer has an inner diameter same as the bearing. 
     
     
       14. The method of  claim 6 , wherein the bearings are installed in an inner hole of the bearing seat. 
     
     
       15. The method of  claim 14 , wherein the bearings are selectively installed by bonding, pressing, or welding.